1. Technical Field
The present invention relates to an electro-optical device in which generation of an optical leakage current in a liquid crystal device due to diagonal light included in a light beam from a light source is suppressed, thereby preventing generation of irregular image regions due to optical leakage, and a projector and an electronic apparatus including the same.
2. Related Art
Two types of projectors for projecting and displaying an enlarged image on a screen are known. One type is a so-called three-panel projector including a light source, a color separation optical system that separates a light beam emitted from the light source into three light components for red (R), green (G), and blue (B) using dichroic mirrors, three light-modulating liquid crystal devices that modulate the associated separated light components in accordance with image information, and a color-synthesis optical device that combines the light components modulated by the associated light-modulating liquid crystal devices. The other type is a single-panel projector and includes only one light-modulating liquid crystal device and a color generator.
A liquid crystal light valve, which is an exemplary light-modulating liquid crystal device, includes two transparent substrates, such as glass substrates or quartz substrates, and a liquid crystal layer sealed between the two substrates. Active elements such as thin-film transistors (hereinafter abbreviated as “TFTs”) are arranged in a matrix on one substrate, and a counter electrode is arranged on the other substrate, thereby allowing optical characteristics of the liquid crystal layer sealed between the two substrates to be changed according to an image signal to display an image.
The liquid crystal light valve (light-modulating liquid crystal device) structured as described above has no fixture. As disclosed in JP-A-2004-35600, the liquid crystal light valve is accommodated and held in place in a holder made of metal or the like, and the holder is fixed using a fixture such as a screw to an incident end face of the light-synthesis optical device.
In the liquid crystal light valve, irradiation of a channel region or a drain end of each of the TFTs placed on one substrate (TFT array substrate) with strong light induces an optical leakage current and thus changes the characteristics of the TFTs, resulting in uneven image quality, a reduction in contrast ratio, and deterioration of flicker characteristics of a display surface.
To avoid these problems, a light-shielding film (black matrix) for shielding a channel region and a channel-adjacent region of each of the TFTs from light is formed at least in a portion of the other substrate (counter substrate) facing each of the TFTs, thereby preventing the TFTs from being irradiated with strong light.
Recent liquid crystal projectors have a high output lamp as a light source in order to enhance the luminance and the resolution of a projected image, and are also designed to improve the efficiency of using light. With regard to this luminance improvement, the liquid crystal light valve (light-modulating liquid crystal device) has pixels with a large numerical aperture to improve the transmittance of projection light. Also, the number of pixels is increased to enhance the resolution.
The larger the number of pixels, the larger an effective pixel region becomes. This narrows a margin between a window frame of an incident window (through which a light beam is transmitted) bored in a holder that holds the liquid crystal light valve and an end of the effective pixel region of the liquid crystal light valve (hereinafter referred to as an “effective pixel end”), which is orthogonal to a light incident direction, compared with that in a known liquid crystal light valve.
When the margin between the effective pixel end of the liquid crystal light valve and the window frame of the incident window becomes narrower, part of diagonal light included in a light beam emitted from the light source is transmitted to the window frame of the incident window and is reflected therefrom to enter the TFTs, thereby generating an optical leakage current. As a result, irregular pixels in the form of a double cross are often generated near the end of the effective pixel region of the liquid crystal light valve (hereinafter referred to as “optical leakage irregular pixels”).
To avoid such unpleasant effects, the aperture area of the incident window is increased to provide a wide margin with the effective pixel end. In this way, generation of optical leakage irregular pixels can be avoided. Since edge portions of the window frame of the incident window function as fixture surfaces for fixing the incident-side outer periphery of the liquid crystal light valve (light-modulating liquid crystal device), the incident window cannot be enlarged greater than needed to fix the liquid crystal light valve in the holder in a stable state.